Models for the Homogeneous Hydrodesulfurization of Thiophenes: Manganese-Mediated Carbon−Sulfur Bond Cleavage and Hydrogenation Reactions
摘要:
Chemical reduction of a series of (eta(5)-thiophene)Mn(CO)(3)(+) complexes (3a-d) under an atmosphere of CO affords dimanganese metallathiacyclic complexes (4a-d), which have a Mn(CO)(4) moiety regioselectively inserted into a C-S bond. Reaction of 4 with H-2, the rate of which is strongly influenced by substituents on the thiophene ring, leads to hydrogenolysis of the Mn-C sigma-bond and formation of (OC)(3)Mn(mu-H)(mu-SCRCHCHCHR')Mn(CO)(3) (8; R, R' = H, Me), which contains bridging hydride and thiolate ligands and a Mn-Mn bond. The addition of PhMgBr to 3 occurs at the sulfur to give zwitterionic complexes (6a-c, 14), which undergo regioselective hydrogenolysis of a C-S bond and, in some cases, partial desulfurization with concomitant formation of (OC)(4)Mn(mu-H)(mu-SPh)Mn(CO)(4) (5a). Crystal structures are reported for complexes 4b,d, 5a, 8d, 10, 12c, and 14b,c. It is suggested that the reactions reported herein may be relevant to the general problem of hydrodesulfurization (HDS) of thiophenic molecules.
Hydrogenation of (1-phenylthiophene)Mn(CO)3 (thiophene=3-methylthiophene and 3,4-dimethylthiophene) complexes: formation of tetrakis(tricarbonyl-phenylthiomanganese)
the hydrogenation of (1-phenylthiophene)Mn(CO)3 (2), the nature of the thiophene derivatives strongly affect the yields and distribution of reaction products. When 3-methyl- and 3,4-dimethylthiophene were used as thiophene derivatives, the dimer [Mn(CO)4(SPh)]2 (7) and the tetramer [Mn(CO)3(SPh)]4 (8) was obtained as major products and the hydrodesulfurized product, isoprene or 2,3-dimethyl-1,3-butadiene
对于(1-苯基噻吩)Mn(CO)3(2)的氢化,噻吩衍生物的性质强烈影响反应产物的产率和分布。当使用3-甲基和3,4-二甲基噻吩作为噻吩衍生物时,二聚体[Mn(CO)4(SPh)] 2(7)和四聚体[Mn(CO)3(SPh)] 4(8)以主要产物的形式获得了H 2 O 3,并且以高收率获得了加氢脱硫的产品异戊二烯或2,3-二甲基-1,3-丁二烯。X射线衍射研究证实了7和8的结构。